Obsessional disorder of childhood is a disabling illness which remains chronic for about 50% of patients. To date, 27 subjects have been studied, the largest sample of children with this disorder studied prospectively. The purpose of the study is to compare subjects with age-, sex-matched controls on a neuropsychological, psycholinguistic, and familial measures. In addition, a controlled treatment trial with clomipramine is conducted and prospective follow-up of the obsessive compulsive subjects is underway.